A gas turbine engine generally includes a compressor section, a combustion section, a turbine section, and an exhaust section. The compressor section progressively increases the pressure of a working fluid entering the gas turbine engine and supplies this compressed working fluid to the combustion section. The compressed working fluid and a fuel (e.g., natural gas) mix within the combustion section and burn in a combustion chamber to generate high pressure and high temperature combustion gases. The combustion gases flow from the combustion section into the turbine section where they expand to produce work. For example, expansion of the combustion gases in the turbine section may rotate a rotor shaft connected, e.g., to a generator to produce electricity. The combustion gases then exit the gas turbine via the exhaust section.
The turbine section includes one or more turbine nozzles, which direct the flow of combustion gases onto one or more turbine rotor blades. The one or more turbine rotor blades, in turn, extract kinetic energy and/or thermal energy from the combustion gases, thereby driving the rotor shaft. Generally, each of the one or more turbine nozzles includes an inner side wall having a radially outer surface in contact with the combustion gases and a radially inner surface isolated from the combustion gases. Since the radially outer surfaces of each of the inner side walls are in direct contact with the combustion gases, it may be necessary to provide cooling air thereto.
In certain configurations, the gas turbine engine may include systems that direct cooling air onto the radially inner surfaces of the inner side walls. The spent cooling air is typically exhausted through one or more apertures extending through the inner side walls. Nevertheless, apertures defined by the inner side walls are expensive to form and increase the overall cost of the gas turbine engine.